1. Field of the Invention
This invention relates generally to circuit breakers and, more particularly to circuit breakers of the electromagnetic type including an operating mechanism and an operating handle.
2. Background Information
Circuit breakers of the electromagnetic type are shown, for example, in U.S. Pat. Nos. 3,329,913; and 4,151,386.
Such electromagnetic circuit breakers typically comprise a movable contact, which is mounted on a movable arm, and a fixed or stationary contact. An operating handle is coupled to the movable arm via a linkage mechanism, part of which comprises a collapsible toggle assembly. The movable and stationary contacts are operated between contacts “open” and contacts “closed” positions by pivoting the operating handle. The circuit breaker further comprises an electromagnetic device which, in response to one or more predetermined electrical conditions, collapses the toggle assembly to a broken state, in order to electrically trip “open” the separable movable and stationary contacts.
A known magneto-hydraulic circuit breaker employs an early (i.e., relative to handle throw) toggle-on point. At the point where the operating mechanism toggles and the unbroken linkage mechanism begins to move, there is very little energy stored in the operating mechanism springs. As a result, the circuit breaker can be “teased” on, which causes undesirable and potentially damaging arcing to the separable contacts.
“Slow make” is defined as the closing velocity of the circuit breaker separable contacts being directly dependent upon the closing speed of the operating handle. For a circuit breaker operating at relatively high voltages (e.g., 480 to 600 VAC), this results in a greater tendency for the separable contacts to weld closed, and significantly reduces the number of switching operations in the operating life of the circuit breaker.
U.S. patent application Ser. No. 10/185,858, filed Jun. 27, 2002, discloses a circuit breaker including a pivot lever having a first arm with a first end adapted for engagement with a movable contact arm, and a second arm having a second end adapted for engagement with an operating handle assembly. The first end of the pivot lever carries a U-shaped hook member pivotally disposed thereon. The hook member has a J-shaped hook, which is adapted for engagement with the movable contact arm, and a J-shaped pivot end, which is pivotally mounted in an opening of the first arm. In order to eliminate the dependency between the movable contact arm and the operating handle assembly, the J-shaped hook initially hooks the movable contact arm. The pivot end of the hook member is inserted into the first or free end of the pivot lever. The pivot lever pivots about a pin and translates the hook member and the movable contact arm movement up to the operating handle assembly. The second or handle end of the pivot lever interacts with a blocking disk of the operating handle assembly, which disk rotates about the same center as the operating handle, but is allowed independent movement.
There is room for improvement in circuit breakers.